Static and dynamic pressure compensation for intake oxygen sensing

Abstract

An oxygen sensor pressure compensation system includes a static pressure compensation module to receive an oxygen sensor signal from an oxygen sensor and a pressure signal from a pressure sensor and to perform static pressure compensation. A dynamic pressure compensation module receives the oxygen sensor signal and the pressure signal and to perform dynamic pressure compensation. A summing module generates a compensated oxygen signal based on the static pressure compensation and the dynamic pressure compensation.

What is claimed is:   
     
       1. An oxygen sensor pressure compensation system, comprising
 a static pressure compensation module configured to (i) receive an oxygen sensor signal from an oxygen sensor and a pressure signal from a pressure sensor, (ii) retrieve a correction factor based on the pressure signal, and (iii) apply the correction factor to the oxygen sensor signal to generate a static pressure compensation signal, wherein the static pressure compensation signal corresponds to a static pressure as measured by the pressure sensor; 
 a dynamic pressure compensation module configured to (i) receive the pressure signal, (ii) generate a dynamic pressure compensation signal based on the pressure signal, wherein the dynamic pressure compensation signal corresponds to a change in the pressure signal from a previously received pressure signal; and 
 a summing module to configured to combine the static pressure compensation signal and the dynamic pressure compensation signal to generate a compensated oxygen signal. 
 
     
     
       2. The oxygen sensor pressure compensation system of  claim 1 , further comprising a response rate matching module connected to the oxygen sensor, the pressure sensor, the static pressure compensation module and the dynamic pressure compensation module, wherein the rate matching modules is configured to match a response rate of the oxygen signal and the pressure signal. 
     
     
       3. The oxygen sensor pressure compensation system of  claim 2 , wherein the response rate matching module includes a first filter to receive the oxygen signal and a second filter to receive the pressure signal. 
     
     
       4. The oxygen sensor pressure compensation system of  claim 3 , wherein the first and second filters are first order filters with different constants. 
     
     
       5. The oxygen sensor pressure compensation system of  claim 1 , wherein the static pressure compensation module includes:
 a first lookup table to convert the oxygen signal to an oxygen percentage signal; and 
 a second lookup table to receive the pressure signal and to generate the correction factor. 
 
     
     
       6. The oxygen sensor pressure compensation system of  claim 5 , wherein outputs of the first lookup table and the second lookup table are input to:
 a summer to generate the static pressure compensation signal; or 
 a multiplier to generate the static pressure compensation signal. 
 
     
     
       7. The oxygen sensor pressure compensation system of  claim 1 , wherein the dynamic pressure compensation module includes:
 a first lookup table to receive the pressure signal and to generate a derivative of the static pressure compensation signal; 
 a delay circuit to receive the pressure signal; 
 a difference circuit to receive an output of the delay circuit and the pressure signal and to generate the change in the pressure signal, wherein the output of the delay circuit corresponds to the previously received pressure signal; and 
 a multiplier to receive a constant, an output of the difference circuit and an output of the first lookup table and to generate the dynamic pressure compensation signal. 
 
     
     
       8. The oxygen sensor pressure compensation system of  claim 1 , further comprising a smoothing circuit to perform smoothing of the compensated oxygen signal. 
     
     
       9. A vehicle comprising:
 an intake manifold, wherein the oxygen sensor and the pressure sensor are arranged in the intake manifold; and 
 the oxygen sensor pressure compensation system of  claim 1 . 
 
     
     
       10. A vehicle comprising:
 an exhaust system, wherein the oxygen sensor and the pressure sensor are arranged in the exhaust system; and 
 the oxygen sensor pressure compensation system of  claim 1 . 
 
     
     
       11. A method compensating an oxygen sensor for pressure variations, comprising
 receiving an oxygen sensor signal from an oxygen sensor and a pressure signal from a pressure sensor; 
 retrieving a correction factor based on the pressure signal; 
 applying the correction factor to the oxygen sensor signal to generate a static pressure compensation signal, wherein the static pressure compensation signal corresponds to a static pressure as measured by the pressure sensor; 
 generating a dynamic pressure compensation signal based on the pressure signal, wherein the dynamic pressure compensation signal corresponds to a change in the pressure signal from a previously received pressure signal; and 
 combining the static pressure compensation signal and the dynamic pressure compensation signal to generate a compensated oxygen signal. 
 
     
     
       12. The method of  claim 11 , further comprising matching a response rate of the oxygen signal and the pressure signal. 
     
     
       13. The method of  claim 12 , further comprising using a first filter to receive the oxygen signal and a second filter to receive the pressure signal. 
     
     
       14. The method of  claim 13 , wherein the first and second filters are first order filters with different constants. 
     
     
       15. The method of  claim 11 , further comprising:
 using a first lookup table to convert the oxygen signal to an oxygen percentage signal; and 
 using a second lookup table to receive the pressure signal and to generate the correction factor. 
 
     
     
       16. The method of  claim 15 , wherein outputs of the first lookup table and the second lookup table are input to:
 a summer to generate the static pressure compensation signal; or 
 a multiplier to generate the static pressure compensation signal. 
 
     
     
       17. The method of  claim 11 , further comprising:
 generating a derivative of the static pressure compensation signal; 
 delaying the pressure signal, wherein the delayed pressure signal corresponds to the previously received pressure signal; 
 generating the change in the pressure signal based on the delayed pressure signal and the pressure signal; and 
 generating the dynamic pressure compensation signal based on a constant, the change in the pressure signal, and the derivative of the state pressure compensation signal. 
 
     
     
       18. The method of  claim 11 , further comprising performing smoothing of the compensated oxygen signal. 
     
     
       19. The method of  claim 11 , further comprising arranging the oxygen sensor and the pressure sensor are arranged in an intake manifold of an engine. 
     
     
       20. The method of  claim 11 , further comprising arranging the oxygen sensor and the pressure sensor are arranged in an exhaust system of an engine.